Approach control apparatus for



APr 29, 1941"- H. G. BLossl-:R Re. 21,783

APPROACH CONTRQL APPARATUS FOR RAILWAY -SIGNALING SYSTEMS riginal FiledJuly 29, 19158 3 Sheets-Sheet l INVENTOR Herm .Blossel BY 2 i L.;ATTORNEY April 29, 1941. H. aaLossER Re- 21,783

APPROACH CONTROL APPARATUS FOR RAILWAY SIGNALING SYSTEMS 3 Sheets-Sheet2 Original Filed July 29 .195?.

||||L QU INVENTCR Herm BY G Blossel KQ, ATTORNEY April 29, 1941. H. G.BLossER 'Re- 21,783 ?PROACH CONTROL APPARATUS FOR RAILWAY SIGNALINGSYSTEMS Original Filed July 29, 1938 3 Sheets-Sheet 5 Willi;

L11 ATTOR N EY Reissued Apr. 29, 1941 APPROACH CONTROL APPARATUS FORRAILWAY SIGNALING SYSTEMS Herman G. Blosser, Pittsburgh, Pa., assgnor toThe Union Switch & Signal Company, Swissvale,- Pa., a, corporation ofPennsylvania riginal No. 2,174,255, dated September 26, 1939, Serial No.222,014, July 29, 1938. Application for reissue September 25, 1940,Serial No.

23 Claims.

My invention relates to approach control appparatus for use in railwaysignaling systems of the coded track circuit class and it has specialreference to the employment of such app-aratus for approach controllingvarious signaling functions without they use of line wires.

Generally stated, the object of my invention is to improve certainfeatures of an approach control without line wire scheme wherein therails of each unoccupied signal block length of track transmit code steppulses of auxiliary energy forwardly from the block entrance to effectthe energization of a slow release approach relay at the block exit.

A more specific object is to supply the referred to pulses of auxiliaryenergy tothe entrance end of each track circuit in an improved mannerwhich does not interfere with the normal code following operation of theassociated signaling system track relay and which -eliminates wastage ofpower at the location of that relay.

Another object is to receive these pulses at the exit end .of the track:circuit and to4 energize the associated slo-w release approach relay instep with them in a novel manner which reduces the l necessary delayperiod of that relay and thereby quickens its response to the entry of atrain into the signal block.

An .additional object is to provide for a double functioning of thecontacts of the track circuit coding devices in their control of thecombined signaling and approach governing equipment which is installedat the exit end of each signal block.

A further object is to extend the length of the track circuit which thenon line wire apparatus herein disclosed is capable of approachcontrolling without the aid of cut section facilities.

A still further object is to provide cut section facilities which aresuitable for use with approach control schemes which embody my improvedfeatures.

In practicing my invention I attain the above and other objects and`advantages by transferring the entrance end connection of the trackcircuit from the signaling system track relay to a source of auxiliaryenergy at the beginning of each off code period and returning it lto thetrack relay before the beginning of the next on period; by providing theexit end of each track circuit with a code following detector relaywhich is operated by auxiliary energy received from the rails, which isequipped with a supplemental stick circuit and other special releasedelaying means, and which locally controls the energization of theassociated slow release approach relay; by carrying the pick-up and thestick circuits of the detector relay through separate contacts of thesignaling system coding device and so arranging these twoy lcontactsthat they act in parallel in making and breaking'the circuit over whichthe rails receive coded signal control energy; and by interposing asensitive code following pilot relay between the rails and `themulti-contact code following track relay which is operated by entranceend energy received therefrom.

I shall describe a few forms of approach control apparatus embodying myinvention and shall then point out the novel features thereof in claims.These illustrative embodiments are disclosed in the accompanyingdrawings in which:

Fig. l is ak diagrammatic represent-ation of a single section of railwaytrack which is equipped with one preferred form of my improved non linewire approach control equipment;

Fig. 2 is' a diagrammatic view of cut section facilities which aresuitable for use with the approach control scheme of Fig. 1;

Fig. 3 is a diagram showing entrance end facilities supplemented toincrease the length of the track circuit which may be approachcontrolled without the aid `of cut section facilities;

Fig, 4 is-a similar representation of exit end facilities which includeprovision for a double functioning of the contactsof the signalingsystem coding device;

Figs. 5 and 6 are diagrammatic showings of signal location equipments inwhich myY improv-ed approach control apparatus is combined with twodifferent forms of signaling system decoding apparatus; and

Figs. 7 and 8 are similar views of fur-ther forms of cut sectionfacilities which areV suitable for use with the approach control schemesdisclosed herein.

In the several views of the drawings, like reference charactersdesignate corresponding parts. Referring first to Fig. 1, the improvedapproach control apparatus of my invention is there disclosed inassociation with a coded track circuit system of automatic blocksignaling for a railway track |-2 over which it will be assumed thattraiiic moves in the single directionindicated by the arrow, or fromleft to right in the diagram. The protected stretch of this track isdivided into the customary successive sections by insulated rail joints3 and the rails of each section form a part of a track circuit to whichcoded signal control energy is supplied in customary manner.

In this View of Fig. 1, vreference characters D and E respectivelydesignate the entrance and the exit ends of one of these track sectionswhich is illustratively shown as being a full signal block in length;character TR designates a code following track relay which is installedat the entrance f guards the entrance of each of the track blocks andwhich is controlled by the associated track relay TR through the mediumof decoding apparatus I0.

An automatic block signaling system of the referred to coded trackcircuit type operates without the aid of line Wires and inrepresentative form it includes all of the elements above named. Such asystem further comprises the customary facilities (not shown in Fig. 1)for continuously operating each of the exit end relays CR at one oranother of the usual plurality of distinctive code rates. Selectionamong these rates (which in a typical three indication system mayconsist of 75 and 180 energy pulses per minute) is made in accordancewith advance traiic conditions by the decoding apparatus I functioningin customary manner.

This decoding apparatus (details not shown in Fig. 1) is controlled inthe usual fashion by the associated track relay TR and it performs thefurther function of selectively setting up a lighting circuit for one oranother of the lamps (G, Y and R in the typical three indication systemabove referred to) of the Wayside signal S at the same location. In thearrangement represented these signal lamps derive energizing currentfrom a power source which is designated by the terminals plus and minusFor applications in which train carried cab signals (not shown) also areto be controlled, the representative code signaling facilities may stillfurther comprise means at the exit end of the track circuit foradditionally supplying the rails thereof with coded alternating currentenergy. In the form shown at location E in Fig. 1, such means include atuned alternator TA which at proper times introduces alternating currentenergy of 100 cycle per second or other suitable carrier Wave frequencyinto the rail supply circuit which coding contact 5 of device TRcompletes during each energy on period of the direct current signalcontrol code from battery TB.

In order that certain functions of the signaling system may be renderedactive only upon the approach of a train, the apparatus installed ateach of the signal locations D, E etc. is supplemented by an approachrelay AR which is arranged to maintain the referred to functionsinactive at all times except when the section of track to the rear ofthe location becomes occupied. In the illustrative arrangement Which isshown at location E in Fig. 1, these approach control functions consistin lighting the wayside signal Se (normally dark) and in supplying therails of the track section to the rear of that signal with codedalternating current energy for cab signal control.

The former function is governed by a contact 9 of the approach relay ARand the latter by a companion contact II thereof. Either of thesefunctions may, of course, be controlled individually by the approachrelay and it will be apparent, moreover, that signaling functions otherthan or in addition to those just named may likewise be governed by thesame relay.

When applied to coded signaling systems of the conventional characterjust considered, the improved approach control apparatus hereindisclosed renders the relay AR at each signal location responsive to theapproach of a train and does this, moreover, without the use of linewires. For each of the signal blocks this approach control apparatuscomprises: (1) entrance end facilities which supply the rails of thatblock With pulses of auxiliary energy which are in step with recurringperiods of the signal control code, and (2) exit and facilities whichreceive these auxiliary pulses from the rails and energize the appreachrelay AR in step with them.

In the form shown at location D, Fig. 1, the referred to entrance endfacilities comprise a battery or other source of auxiliary energy AB, animpulse relay IR for transferring the connection of the track rails Iand 2 from the track relay TR to battery AB during each 01T period ofthe received signal control code, and means including a transformerwinding 8 for supplying the relay IR with a pulse of pick-up energy atthe beginning of each of the named off periods.

This relay supply Winding 8 may, as shown in Fig. 1, be a part of theusual signaling system decoding transformer DT2 or, as shown in Figs. 2,3, 5, 6 and 7, it may form a part of a separate relay transformer RT. Ineither case the transformer (DT or RT) is provided with a primaryenergizing circuit which is controlled by a contact I2 of the codefollowing track relay TR and which derives energy from a direct currentsource designated by the terminals plus and minus Each time that thetrack relay releases the pole changing action of this contact I2 causesto be induced in the secondary winding 8 a pulse of transformer voltagehaving the polarity designated by the small arrow and which forconvenience will be referred to as normaL Each time, however, that thetrack relay picks up the reverse action of the contact I2 causes to beinduced in this winding 8 a pulse of transformer voltage of the oppositeor reversed polarity.

Both half waves of voltage from winding 8 are impressed upon theoperating winding ofthe impulse relay IR. This relay, however, is of thepolar type and contact I3 thereof occupies the released position (shownin full lines) as long as the relay remains denergized or receivescurrent of the reversed polarity just described. In that position thecontact connects the operating winding of the track relay directlyacross the track circuit rails I and 2.

When, however, relay IR receives from winding 8 the beforernentioneclpulse of normal polarity energy, it picks up contact I3 and therebydisconnects relay TR from the track rails and connects the auxiliarybattery AB thereacross. In this manner each release of the track relayTR causes the impulse relay IR momentarily to transfer the track railconnection from the winding of track relay TR to the output circuit ofbattery AB. At the same time, each pick-up of the track relay isineffective for interfering with the normal connection. of the railswith the winding of that relay.

In the forin shown at location E in Fig. 1, my improved exit endfacilities comprises a detector relay KR which responds to pulses ofauxiliary energy received over the rails I and 2 from battery AB, acircuit controlled by a contact I of that relay for energizing theapproach relay AR from a local source designated by the terminals plusand minus, and means for making the relay AR sufficiently slow releasingto bridge the intervals between recurrent responses of the detectorrelay.

This detector relay KR is of the code following type and the operatingwinding thereof is connected in energy receiving relation with the trackrails I and 2 only during the oi'l periods of the signal control codewhich contact 5 of device CR produces. The here represented arrangementof devices CR, KR and AR is similar to that disclosed and claimed in acopending application Serial No. 221,317, led July 26, 1938, by EdwardU. Thomas; in this arrangement the rst named connection is completed bythe coding contact 5 when in its uppermost or off period position.

The slow release approach relay AR may be energizedin step with theresponses of the detector relay KR in any suitable manner. As shown, thecontact I5 of the detector relay is directly included in a local directcurrent energizing circuit for the operating winding of the approachrelay. For delaying the release of this relay AR and thereby enabling itto remain continuously picked up as long as its winding receives codestep pulses of the named energy, use may, of course, be made of anysuitable means such as a snubbing impedance (not shown) or internaldesign expedients incorporated in the relay. Because of their well-knowncharacter, all of the drawing views except Figs. 5 'and 6 make noattempt to represent any such means.

The function of the exit end tuned alternator TA which is shown atlocation E in Fig. l is to generate locally from a direct currentsourcethe alternating current energy which at times is required for cab signalcontrol. sented this alternator includes a transformer I'I whichreceives primary energizing current from the direct current terminalsplus and minus through a circuit which is periodically pole changed by areed type of vibrating member I8.

This member may be of iron or other magnetic material and is designed tohave a natural rate of vibration which corresponds to the 100 cycle persecond or other desired frequency of the output voltage of thealternator TA. Driving movement is imparted thereto by an electromagnetI9 having an energizing circuit which is completed at point 20 each timethat the reed occupies its lowermost position. In this manner thearmature is caused to vibrate at its natural rate as long as the drivingcircuit therefor is connected with a source of energy.

When in its lowermost position the armature sets up a circuit throughwhich current from the referred to direct current source flows in onedirection through the right portion of the primary winding of thetransformer I1 and when in its uppermost position the reed completes asimilar circuit through Which current flows in the opposite directionthrough the left portion of the transformer winding and to the negativesupply terminal by Way of a mid tap 23. Each complete vibration of thearmature IB thus causes a cycle of alternating current voltage to beinduced in the secondary Winding of the transformer I l.

In this manner an electromotive force of the 100 cycle or other cabsignal control frequency is generated Whenever the approach relay ARreleases its contact Il and thereby connects the In the form repreialternator supply conductor 24 with the plus terminal of the localdirect current source. Conveniently, this source may take the form ofthe same local battery (not shown) which supplies lighting current tothe signal lamps.

It will be seen, therefore, that in a system of the improved characterwhich is shown in Fig. 1, no line wires whatever are required betweensignal locations. The control of the wayside signals S is effectedthrough the medium of coded signal control energy transmitted throughthe track rails I and 2 in conventional manner; the control of theapproach relays AR is similarly effected through the medium of oifperiod pulses of auxiliary energy from battery AB fed forwardly to thesection exit; and the supply of the alternating current coded energy forcab signal control is provided through the tuned alternator TA from thetrack battery TB or other local source of direct current energy.

In operation of the nonline wire approach control facilities which arerepresented in Fig. 1, the track rails I and 2 of section D-E act in theusual manner to transmit energy from one end of the section to the otheras long as the section remains unoccupied. Each time, under suchconditions, that contact 5 of the coding device CR is in the lowermostor on code period position the track battery TB picks up the track relayTR over a circuit which may be traced from the positive terminal of thebattery through secondary winding of transformer I'l, conductor 26, acurrent limiting impedance 21, back contact 5 of device CR, conductor28, track rail I, conductor 29, the Winding of the track relay TR,conductor 3 I, back contact I3 of relay IR, conductor 32, the track rail2, and conductor 33 back to the negative terminal of battery TB.

Each time that the coding contact 5 occupies the uppermost or off codeperiod position and bridges the winding of the detector relay KR acrossthe track rails, the track relay TR at the entrance end of the sectionreleases and transfers the primary energizing circuit for transformerDTZ from conductor 35 and the upper half of the transformer primary toconductor 36 and the` lower half of the primary. This reversal ofexcitation induces in the secondary winding 8 of the transformer a pulseof normal polarity voltage which is impressed on the winding of theimpulse relay IR o-ver a circuit eX- tending from the lower terminal ofwinding 8 through conductor 31, the winding of relay IR and conductor 38back to the upper terminal of the transformer secondary.

In responding, contact I3 of relay IR picks up at the beginning of eachof the olf periods of the signal control code and disconnects thewinding of relay TR from the track rails and connects the auxiliarybattery AB thereacross. Under this condition the battery AB picks up thedetector relay 'KR at the exit end of the section over a circuit whichmay be traced from the positive terminal of the battery through acurrent limiting impedance 40, front contact I3 of relay IR, conductor32, track rail 2, conductor 33, the winding of relay KR, conductor 4I,front contact 5 of device CR, conductor 28, track rail I, and conductors29 and 42 back to the negative terminal of battery AB.

Under the influence of each of these auxiliary pulses of energy receivedfrom the trackway, contact l5 of code following detector relay KR picksup and completes for the approach relay AR a local energizing circuitwhich may be traced from the positive termin-al of a suitable supplysource through front contact I5, conductor 43 and the winding of relayAR back to the negative terminal of the supply source.

As a result of these recurring pulses of local energization, the slowrelease approach relay AR. now holds contacts 9 and II continuouslypicked up, thereby maintaining the Wayside signal Se and the tuned reedvalternator TA at location E deenergiaed as long as the track sectionD--E remains Vacant.

In the event :that a train comes into the track section D-E, the usualshunting action of its Wheels Vand axles reduces to a very low value thepotential difference between the rails I and 2 and thus deprives both ofthe relays TR and KR of pick-up energy. Relay KR now remains releasedcontinuously and the supply of local energization to `the approach relayAR is discontinued. In consequence, contacts Q and II of that relay nowcomplete energizing circuits for signal Se and the tuned reed alternatorTA.

As a result the named Wayside signal now lights the particular lampselected by the decoding equipment II) and the tuned reed alternator TAsupplies the rails of track section D-E with a pulse of alternatingrcurrent energy each time that the Contact 5 of device CR occupies itslowermost position. As has been mentioned this energy is suitable forthe control of train carried calo signals and the circuit over which itis supplied may be traced from the right terminal of the secondarywinding of transformer Il through conductor 26, impedance 27, backcontact 5 of device TR, conductor 28, track rail I, the wheels and axles(not shown) of the train, rail 2, conductor 33, and track battery TBback to the left erminal of the transformer secondary.

As soon as the rear of the departing train clears the exit of sectionD-E the coded energy from track cattery TB is again transmitted by therails to the track relay TR at the section entrance. That relay oncemore responds and the operation of contact I2 thereof causes theinipulse relay IR again to connect the track rails in energy receivingrelation with the auxiliary battery AB during each of the olf codeperiods. These auxiliary energy pulses are, in turn, transmitted by therails to the detector relay KR at the exit location E.

In responding to them. that relay again causes the approach relay AR toreceive recurrent pulses of local energizing curren The approach relayonce more picks up and due to its slow releasing characteristicscontinuously deenergizes the wayside signal Se and the tuned reedalternator TA at location El, thereby restoring both of these devices totheir normally inactive state.

Further regarding my improved entrance end facilities which are shown atlocation E, the irnpulse relay IR and the transformer winding 8 fromwhich it receives pick-upi energy are so designed that the rela-y willpick up contact I3 relatively soon after the beginning' of each odperiod of the received signal control code and will maintain thiscontact picked up until just before the beginning of the on period forthe particular code wherein the periods are shortest. In the oase of thethree indication signaling system referred toin an earlier portion ofthis specification, this limitation in the length of pick-up time forthe contact I3 will, of course, be determined by the highest speed or180 energy llulse per minute code. Such a code has a cycle length of3%00 second and an off period length of about 1%00 second.

With this 180 energy pulse per minute code, it is foundA possible tomaintain the impulse relay contact I3 picked up for a. total ofapproximately 7100 second during each of the .off periods. This allows amargin of approximately 5A@ second from the time that the track relay TRfirst starts to release until the impulse relay IR. fully picks up and aperiod of approximately the same length from the time that the impulserelay IR starts to release until the track relay picks up at thebeginning ofthe next on code period. Such a relation assures about themaximum practical time of connection of the auxiliary battery AB withthe track rails during each off period of the 180 code Wit-houtproducing overlapping or delay in the reconnection of the winding of thetrack relay TR with the rails until after the beginning of thesucceeding on period.

As has been pointed out, the impulse relay IR is preferably of apolarized design and may satisfactorily be of a normally quick actingtype in both the pick-up and the drop-out directions. Even though thepulse of normal polarity energy supplied through transformer winding 8at the beginning of the oif period may be much shorter than the %00second total time of relay pick-up, the desired delay in release isprovided through the snuobing action of the winding 8 which, throughconductors 31 and 38, is directly bridged across the terminal of therelay winding.

Once selected to meet the limiting conditions of the highest speed codeof the signaling system, the relay IR provides the same fixed period ofrail connection transfer for all other codes. That is, even with thelower speed or 75 pulse perI minute code previously referred to, theperiod of rail connection transfer will still be approximately (V secondeven though the total length of the '75 code "oi period is of the muchextended order of *L9/100 second.

In all cases, however, my entrance end facilities afford an improvedmeans for introducing the pulses of auxiliary energy into the trackcircuit without interfering with the normal code following operation ofthe signaling system track relay TR. From a standpoint of energyconservation, these facilities are of special advantage since theymaintain the auxiliaryenergy supply circuit completely disconnected fromthe track rails during the on code periods, and thereby enable the trackrelay TR to receive the full value of trackway energy available at itspoint of connection with the rails. Moreover, during each of the offcode periods, the facilities maintain the track relay TR completelydisconnected from the rails and thus allow all of the auxiliary energyfrom battery AB to be impressed upon the track circuit for-the purposeof transmission forwardly to the operating winding of the code followingdetector relay KR at the section exit.

Considering further my improved exit end facilities which include thisdetector relay KR and of which the tuned reed alternator TA also forms apart in the arrangement of Fig. 1, the secondary winding of thealternator transformer' II is designed w'ith a sufficiently lowresistance as not to interfere objectionably with the transmission ofdirect current from the battery TB to the rails I and 2. The winding ofthe detector relay KR, moreover, is connected with the rails only duringthe oif code period produced by device CR and in this way it isprevented from diverting from the trackway the coded signal controlenergy from either or both of the sources TB and T'A.

Similarly, vsince these sources are disconnected from the rails duringeach oir period of the code which device CR produces, the circuitsthereof do not divert from the operating winding of relay KR theauxiliary energy received over the rails I and 2 from the battery AB. Inthis manner maximum utilization of the different forms of energy for theparticular purposes intended is at all times assured.

Preferably, the resistance of the winding of the detector relay KR iskept relatively low in order that the undesirable effects of trackstorage of the signal control energy from the track battery TB may becounteracted during the off code periods when contact connects thatwinding across the rails. As is known, such energy tends to accumulatein the rails and ballast of each of the signaling system track circuitsas a result of the repeated application thereto of the direct currentcode pulses from th-e track battery or other direct current source ateach section exit. Unless counteracted, the potential appearing betweenthe rails I and 2 because of this storage effect may, over a period oftime, build up to a value which becomes suflicient even to prevent thesignaling system track relay TR at the section entrance from releasingduring the off periods of the signal control code.

The counteracticn of track storage energy which is referred to aboveresults from the low resistance rail discharge path which the winding ofrelay KR provides during each of the off code periods when contact 5 ofdevice CR connects it across the rails I and 2. This shunting actionassures that the rail potential will be Sufliciently reduced at thebeginning of each olf period to enable the entrance end track relay todrop out promptly in the desired manner.

'If desired the basic counteracting provision just described may besupplemented by poling the auxiliary battery AB oppositely to the trackbattery TB. Such an arrangement is shown in Fig. 1 wherein the exit endtrack battery TB makes rail I positive with respect to rail 2 each timeit is connected to the rails over coding contact 5, while the entranceend auxiliary battery AB makes rail 2 positive with respect to rail Ieach time that it is connected to the track circuit by transfer contactI3 of the impulse relay IR. Hence, the olf period pulses of auxiliaryenergy provide a direct counteracting influence which further reducesthe potential of track battery polarity which remains between the trackrails following each disconnection of the battery TB therefrom.

Referring to Fig. 2, I have there represented cut section facilitieswhich are suitable for use with the approach control scheme of Fig. 1.These facilities are required when, because of |excessive length or forany other reason, it becomes necessary to sub-divide the main signalblock length of track into two or more track circuits. In Fig. 2 onelocation of such a sub-division is designated by the character Da and tofacilitate explanation it will be assumed that this particular locationis constituted by interposing insulated rail joints 3 between the limitsD and E of the signal block of Fig. 1.

The facilities of Fig. 2 are arranged to perform three functions. Firstthey repeat the coded direct current signal control energy receivedfromthe forward section rails around the joints 3 and Da. Aiding in this rstfunction is a code follow- .ing track relay TR which is operated byenergy received from the forward section rails, a track battery TB whichserves as anenergizing source for the rails of the rear section, and acoding contact 5 operated by the relay 'I'R and arranged to complete therail supply circuit for the rear section each time that the track relayTR releases and to interrupt it each time that the relay is picked up.

This arrangement of Fig. 2 employs what will be termed as back contactcoding--from the fact that..each off period of the forward section codeproduces an on period in the rear section code while each on period ofthe forward code is accompanied by an off period in the rear code. As inthe corresponding facilities of Fig. 1, the referred to` rail supplycircuit of Fig. 2 may be traced from the positive terminal of battery TBthrough the secondary winding of transformer Il of the tuned reedalternator TA, conductor 26, impedance 21, back contact 5 of device TR,conductor 28, track rails I and 2 and conductor 33 back to the negativeterminal of battery TB.

The second function performed by the cut section facilities of Fig. 2 isto introduce the olf code period pulses of auxiliary energy into therails of the track section ahead of location Da. Participating in thissecond function is an auxiliary battery AB, an impulse relay IR which(as in Fig. 1) transfers the rail connection from the Winding of thetrack relay TR to battery AB, and a transformer RT which supplies relayIR with a pulse of pick-up energy at the beginning of each olf codeperiod.

Each time that the track relay TR releases, contact I2 thereofinterrupts the direct current exciting circuit for transformer RT andcauses winding 8 thereof to supply relay IR with a pulse of normalpolarity pick-up energy. Contact I3 now transfers the normal connectionof the rails I and 2 from the operating winding of relay TR to theterminals of the auxiliary battery AB and thus supplies the auxiliaryenergy to the trackway in the manner named.

The third function performedby the cut section facilities of Fig. 2 isto supply the rails of the track section to the rear of location Da withcoded alternating current energy suitable for cab signal controlwhenever a train enters that rear section. Aiding in this third functionis a tuned reed alternator TA, a slow release approach relay AR forconnecting this alternator with a direct current supply source overcontact II, and a code following detector relay KR for energizing (overcontact I5) the approach relay in step with the pulses of auxiliary oroff code period energy which are received from the rear section rails.

As long as these pulses continue to be received relay AR is periodicallyenergized, as in the system of Fig. 1, and holds contact II picked up tomaintain the alternator TA inactive.` When, however, a train comes intothe rear section, relay KR continuously releases, relay AR becomesdeenergized continuously and the alternator then is connected with thedirect current operating source over conductor 24 and relay contact II.Each time, now, that coding contact 5 of relay TR occupies the lowermostposition the transformer I'I of the apparatus TA impresses IBB cycle orother cab signal control frequency energy upon the rear section rails Iand 2 by way of the circuit previously traced as including conductors 28and 33.

It will thus be seen that the cut section facili- `ties of Fig. 2 may beinterposed within the limits of a signal block length of track, such asshown I and 2.

at D-E in Fig. 1, without interfering with the operation either of themain signaling scheme or of the approach control vfacilities of rnyinvenltion which are used therewith. If desired (not shown Iin Fig. 2)the relative polarity of the two track the type represented in Fig. 1without resorting to cut section facilities. of any kind.

With the basic form of arrangement which is shown at location D in Fig.1, the track relay TR must be provided with a number of contacts. Onesuch contact is shown at I2 in each of Figs. 1 and 3 and two additionalones are represented at 45 and 4G in Fig, 3.

Such additional contacts N are occasioned by the previously referred todecoding apparatus It) one ytypical form of which is shown in greaterdetail in Fig, 5. There the contacts 45 and 45 are included in theprimary and the secondary circuits of a decoding transformer DTI bywhich decoding relays DR'IS and DRI85 of the signaling system `areenergized in a manner more completely to be described later.

The effect of this multiplicity of contacts is to cause the track relayTR to reduire an increased amount of operating energy from the trackrails When the length of the track circuit exceeds say a mile or a mileand a half, difiiculty frequently is experienced in transmitting thenecessary amount of relay operating energy from the track battery TB atthe exit end over the` rails I and 2 to the track relay TR at theentrance end of the signal block and in the past it has been necessaryto resort to cut section facilities (see Fig. 2) for all signal blockswhich have lengths of the order of 2 miles or more. This interposedequipment at the cut section adds, of course, to the total cost of theinstallation and in other respects is considered undesirable.

To make its use unnecessary and to operate the the multi-contact trackrelay TR by means of the comparatively weak signal control energy whichis available at the entrance end of an eX- ceedingly long track circuit,I have provided the extended facilities which are shown in Fig. 3. Theseinclude all of the bas-ic portions of equipment which have beendescribed in connection with location D of Fig. 1 and in addition theyutilize a pilot relay PR which is interposed between the track rails Iand 2 and the operating winding of the code following track relay TR.

This pilot'relay need not be provided with but a single Contact 47 andhence may be designed to pick up on a much smallerintensity of trackwayenergy than can the multi-contact track relay TR. Relay PR is of thecode following type and its operating winding is connected in energyreceiving relation with the rails I and 2 by way of conductors 29 and 32and the transfer contact I3 of the impulse relay IR. Each time that thepilot relay is picked up contact 41 6 thereof completes a localenergizing circuit for the operating winding of the associated trackreiay TR. This circuit may, of course, be supplied from any suitablelocal source land in the arrangement of Fig. 3 the auxiliary battery ABis utilized for this purpose.

In considering the operation of the extended entrance and facilities ofFig, 3, it will be helpful to assume that the rails I and 2 extendingforwardly from location D thereof terminate in cooperating exit endfacilities of the character represented at E in' Fig. l. During suchoperation, each pulse of signal control energy which is received fromthe track rails I and 2 picks up the piiot relay PR over a circuit whichextends from rail I through conductor 29, the winding of relay PR,conductor 3l, back contact I3 of relay IR and conductor 32 back to rail2. In this manner each of the on code periods causes contact 41 of relayTR to pick up the track relay TR over a circuit which may be traced fromthe positive terminal of battery AB through conductor 43, the winding ofrelay TR, front contact 47 of relay TR, and conductors 42 and 29 back tothe negative termin-al of battery AB.

Relay TR is thus caused to follow the trackway code in the same manneras were it to be directly connected across the rails I and 2 as inFig. 1. The contact I2 thereof thus causes transformer RT to supply apulse of normal polarity pick-up voltage to the impulse relay IR at thebeginning of each ofi code period. In responding, relay IR picks upcontact I3 .and thus transfers the track circuit connection from Ithewinding of Ithe pilot relay PR to the output terminals of the auxiliarybattery AB. During each period of such connection transfer, this batterysupplies the rails with a pulse of auxiliary energy over a circuit whichmay be traced from the positive terminal of battery AB through conductor48, impedance 4D, front contact I3 of relay IR, conductor 32, the trackrails I and 2, and conductors 29, 42 and 49 back to the negativeterminalof battery AB.

It will thus be seen that insofar as the coded signaling system and theassociated approach control without line wire scheme are concerned, theextended facilities of Fig. 3 are the full equivalent of the basic formof apparatus shown at location D in Fig. l. As has been pointed out,however, the Fig. 3 equipment has the added advantage of making possiblethe approach control of track circuits of two miles or greater lengthWithout the use of cut section facilities of any kind.

Referring now to Fig. 4, I have there represented an extended form ofexit end facilities which may be substituted for the previouslydescribed exit end apparatus which is represented a-t location E in Fig.l. As in Fig. l, the apparatus of Fig. 4 employs coding, detecting andapproach relay devices CR, KR and AR. II'. differs, however, in .thatthe continuously operating coding device CR2 is provided not only withthe main coding contact 5 but also with a second Contact 50. Likewise,the detector relay designated at KRZ in Fig. 4 has not only the Fig. 1pick-up winding 5I which contact -5 bridges across the track railsduring the off periods of the signal control code, but also a second orstick winding 52 larranged in the manner disclosed andclaimed by thebefore referred to copending application Serial No 221,317 of Edward U.Thomas (filed July 26, 1938) The purpose of this added or stick windingis to make possible a reduction in the period of delay of the approachrelay AR in releasing its cont-acts 9 and II following each prolongedinterruption of its energizing circuit at contact I5 of the detectorrelay KRZ. As is more completely described in the copending applicationjust mentioned, use of a detector relay having such a stick Windingquickens the response of the approach control relay AR to the entry of atrain into the associated track section and thus avoids objectionableflips in the cab signals of a train when that train first passes overthe insulated rail joints 3 at the section entrance.

As shown in Fig. 4, the track battery 'IB is used as the source o-fenergization for the operating winding of the approach relay AR.Moreover, the facilities for supplying the rails with coded alternatingcurrent energy for cab signal control are modified to the extent thatthe tuned alternator represented at TA in each of Figs. 1 and 2' isreplaced by a track transformer TT having a secondary Winding which isserially .included in the rail supply circuit of which battery TB formsa part. At proper times the primary windingA of this transformer isenergized over a conductor 53 from a suitable alternating current sourcedesignated by the terminals B andC.

With such an arrangement, of course, it is imperative that analternating current transmission line be provided along the right-of-Wayfor the purpose of distributing the alternating current energy to eachof the signal locations of which E of Fig. 4 is representative. Asalready pointed out, the use f the tuned alternator TA as in Fig. 1eliminates the need for such a line and allows. all of the signalcontrol and approach governing functions to be carried out without lineWires of any kind and by the aid of energy rderived from the locallyinstalled track and auxiliary batteries TB and AB.

For lowering the impedance which the secondary winding of transformer TTintroduces into 4the rail supply circuit under inactive transformerconditions, the contact II of the approach relay `AR preferably isarranged I(as shown in Figs. 4, 6, '7 and 8) to short circuit theprimary Winding of the transformer whenever the approach relay is pickedup. Thus, whenever the track section to the rear of the location isvacant, this primary shunting path is completed from the lower terminalof the primary of transformer 'IT through conductor 54, front contact IIof the relay AR, and the conductor 63 back to the upper terminal of thetransformer primary.

In operation of the extended exit end facilities of Fig. 4, both of thecontacts 5 and 5I) of the coding device CR2 function in parallel inmaking and breaking the circuit through which the track rails I and 2receive energy from the track battery TB, and also the track transformerTT under certain conditions. Each time that the contacts occupy thelowermost position (shown in full lines), the rails are connected withthe battery TB over a circuit which may be traced from the positivesupply terminal of that battery through conductor 56, contacts 5 and 50in parallel, conductors 59 and 28, the track rails I and2, conductor 33,impedance 21, the secondary of transformer TT and conductor 51 back tothe negative terminal of the track battery.

Each time that the contacts 5 and 5H occupy the uppermost or off codeperiod position, contact 5 connects the pick-up winding 5I of thedetector relay KRZ with the track rails and thus conditions-it forreceiving auxiliary energy therefrom over `a'circuit which extends fromrail 2 through conductors 33 and 58, the relay winding 5I, conductor 4I,front contact 5 of device CB2 and the conductors 59 and 28 back to thetrack rail I. This auxiliary energy, when received, comes from theapproach battery AB of entrance end facilities of the character whichare represented at location D in Fig. 1. In considering the operation ofFig. 4, it will be helpful to assume that the rails I and 2 extendingrearwardly from location E thereof terminate in facilities of thecharacter represented at D in Fig. 1.

In the off code position the second contact of the coding device CR2completes for the stick Winding 52 of the detector relay KRZ a stickcircuit which was set up by a contact EI of the detector relay when thatrelay became picked up by the pulse of auxiliary energy which circulatedthrough the pick-up winding 5I. 'I'his stick circuit functions tocontinue the pick-up of relay KRZ for the full duration of the off codeperiod and it may be traced from the positive terminal of the trackbattery TB through conductor 5B, front contact 50 of device GRZ,conductor 62, front contact 6I of relay KRZ, the winding 52 of thatrelay, and conductors 63 and 51 back to the negative terminal of batteryTB.

In this manner each pulse of auxiliary energy received from the rearduring an off code period picks up the detector relay KRZ and causesthat relay to remain picked up until contact 50 `,of coding device CR2is returned to the lowermost position at the beginning of the succeedingon code period. As lo-ng as the track section to the rear of location E'remains vacant, therefore, relay KRZ responds in this manner during eachoff period and causes contact I5 thereof periodically to complete forthe slow release approach relay AR an energizing circuit which may betraced from the positive terminal of battery TB through conductor 56,front contact I5, the winding of relay AR and conductors 63 and 5l backto the negative terminal of the track battery.

Because of its slow release characteristics the approach relay AR nowholds its contacts 9 and II picked up continuously and thus maintainsthe wayside signal Se and lthe track transformer TT at location E` intheir normally inactive condition.

Upon the entry of a train into the section to the rear of Fig. 4location E, the supply of the auxiliary energy to the detector relay KR2is cut olf due to the usual shunting action of the train wheels andaxles. The detector relay now remains released continuously, relay AR isdeenergized continuously, and it releases contacts 9 and II, therebycompleting the lighting circuit for the wayside signal Se and connectingthe primary winding of the track transformer TT with Vthe alternatingcurrent source B-C.

Each time, now, that the contacts of coding device CB2 are in thelowermost or on code position the secondary winding of this transformersupplies thetrack 4rails with a pulse of alternating current energy byway of a circuit which may be traced from the lower terminal of thetransformer secondary through conductor 51, the track battery TB,conductor 56, contacts 5 and 5I) of device CRZ in parallel, conductors59 and 28, track rail I, the wheels and axles (not shown) of the train,rail 2, conductor 33 and impedance 2l back to the upper terminal of thetransformer secondary.

As soon as the rear of the departing train clears the exit end locationEz, the supply of 01T period pulses of auxiliary energy to the pick-upwinding 5I of the detectorrelay KRZ is resumed, this relay responds andrecurrently completes at contact I5 the energizing circuit for the slowrelease approach relay AR, and that relay once fmore picks up therebyinterrupting at contact 9 the lighting circuit for the wayside signal Seand disconnecting at contact i the track transformer TT from thealternating current source B'-C.

Referring to Fig. 5, I have there represented the equipmertt at lasingle signal location O for a coded track circuit system of automaticblock signaling which provides three indication signal control throughthe use of the 75 and 180 pulse per minute track-way codes previouslyreferred to and which is equipped with lthe improved arpproach controlfacilities herein disclosed. Unlike the earlier views, Fig. representsin relatively complete manner one representative form which thesignaling system decodingk apparatus (indicated at il in Figs. 1, 3 and4) may take.

This decoding apparatus of Fig. 5 includes a decoding transformer DTIprovided with Ia direct current primary exciting circuit which is polechanged in conventional manner by a contact 45 of the code followingtrack relay TR. The secondary winding of this trans-former is connectedin energy supplying relation with a i'lrst decoding relay DRTF5 over acircuit which includes a second or current rectifying contact 46 of thetrack relay. Deriving energy from the exciting circuit of the decodingtransformer through a circuit which includes an extended section 65 ofthe primary winding is a second decoding rela-y DRIBU.

This second decoding relay is rendered responsive only to energizingvoltages from transformer DTI which have la frequency corresponding tothat produced when the track relay TR receives operating energy of the180 pulse per minute code. In the particular arrangement shown, thisselective action is provided throughthe use of a resonant unit DUIBincluded in the supply circuit of relay DRIRE] in well-known manner.

The first decoding relay DR is non-selective and is adapted to pick upwhen the track relay TR responds to operating energy of either the 'l5or the |89 etrackway codes. It is a direct current device and isassociated with the decoding transformer DTI in a manner disclosed andclaimed in copending application Serial No. 210,744, filed by Frank H.Nicholson et al. on May 28, 1938, and assigned to The Union Switch l:Signal Co.

Through themedium of contacts 66 and 61 the two decoding relays DR'E andDR|8D control y., the lighting circuits for the three lamps G, Y and Rof the associated wayside signal So. When relay TR responds to energy ofthe 180 code received from the track section ahead of location O, bothof the relay DR`|5 and DR|80 are picked up to set up the lightingcircuit for the clear lamp G. When this relay responds to energy of the'l5 pulse per minute code, relay DR`|5 only is picked up and thelighting circuit for the approach lamp Y is then set up. Finally whenrelay TR is continuously deenergized, as when a train is in the tracksection ahead of location O, both of the decoding relays DRTS and DR|80are released and the circuit for the stop lamp R is thus set up.

For supplying the track rails with the coded energy already mentioned,the signaling system facilities of Fig. 5 make use of a pair of codetransmitters CTI and CTZ. Device CTI is provided with a contact 'l5which operates at the rate of l5 times per minute while device GT2 isprovided with a similar coding contact |80 which operates at the higherspeed of 180 times per minute. At all times one or fthe other of thesetwo cod-ing contacts is included in the operating circuit of the codingrelay CR2 for the rear signal block.

Selection between the two signal codes is made through the medium of acontact 69 of the decoding relay DR15. When energy of either the 75 or'the 180 energy pulse per minute code is received from the forwardsection by relay TR this contact 69 is picked up and thel coding relayCRZ 'for the rear section then is intermittently energizcd over acircuit which includes coding contact |83 of device CTZ and which may betraced from the positive terminal of a suitable supply source throughcoding contact (in fthe uppermost position), front contact 69 of relayDR'|5, conductor l0, and the winding of relay CR.2 back to the negativeterminal of the supply source.

When no forward section energy is received the relay TR, contact 69 ofrelay DR'l5 is released and the coding relay CRZ for the rear sectionthen is controlled by coding contact 15 by way of a circuit which may betraced from the positive supply terminal through coding contact 'J5 (inits uppermost position) back contact 69 of relay DR'i, conductor 'l0 andthe winding of reiay CB2 back to the negative supply terminal.

In the manner already explained in connection with Fig. 4, contacts 5and 50 of the coding relay CB2 complete a circuit over which the rearsection rails 'are supplied with direct current energy from trackbattery TB each time that the contacts are in the lowermost position andthese same contacts respectively sett up the pick-up Iand stick circuitsfor the detector relay KRZ each time that they are in the uppermostposition. As in Fig. 4 also, the energizing circuit for the slow releaseapproach relay AR at the signal location is controlled by contact l5 ofthe detector relay KRZ.

Completion of this circuit, however, is conditioned upon a contact 'I2of the decoding relay DRH being picked up and connecting conductor 19with the negative supply terminal. This means that the relay AR mustremain released at all times that a train is in the section ahead oflocation O of Fig. 5 regardless of whether a second train is or is notIapproaching the location from the rear. When controlled over backcontact 9 of. relay AR in the manner shown, this insures that thelighting circuit for the wayside signal So can never be interrupteduntil the forward moving train has cleared the exit end of the forwardsection referred to.

In the arrangement of Fig. 5, moreover, the code transmitter CTZ of Fig.5 operates continuously while the 75 code transmitter CT Ireceivesoperating current only when a contact 13 of the decoding relay CR15 isreleased. Since this release takes place only when the section of trackin advance of location O is occupied, the "norme-Led use of Contact 'I3assures that coder CTI will be placed in operation only when needed.

For assisting in the correction of code distortion in the rear trackcircuit, the coding relay CR?! is provided with a snubbing circuit 16which tends to prolong somewhat the time that the contacts 5 and 6remain in the uppermost or off period position during each code cycle.As shown in Fig, 5, furthermore, the approach relay AR is provided witha comparable snubblng circuit Tl. It, however, performs only the beforeexplained function of causing thev relay AR to be suiiciently slowreleasing to bridge the periods between recurrent responses of thedetector relay KRZ when the section of track to the rear of location O`is vacant.

For supplying the rear section rails with alternating current energy forcab signal control, the equipment of Fig. makes use of a tunedalternator TA which functions in the manner already described inconnection with Figs.. 1 and 2. The output terminals of this alternatorreplace the track transformer TT of Fig. 4 and operation of thealternator is controlled by contact II of the approach relay AR whichwhen released connects the alternator input conductor 24 with thepositive terminal of a suitable local direct current supply Source.

In operation of the equipment shown in Fig. 5, the signaling systemportions thereof function in conventional manner While the approachcontrol portions thereof operate in a way which is comparable to thatalready explained in connection with earlier figures of the drav'vings.`Hence, it will suflice `to point out that as long as the protectedstretch of track I--2 remains vacant the exit end facilities for eachsection supply the rails thereof with energy of the 180 coding, theentrance end track relay TR for each section responds to this energy,the assor'z'iat'edv decoding relays DR and DRIBD at each signal locationare both picked up, the "'clear lamp G of the controlled wayside signalS has' its lighting circuit set up and contact |80 of Adevice CTZ is'included in the energizing circuit of the coding relay CB2 for .thetrack section to the rear.

Each release of the track relay TR causes the impulse relay IR to pickup and momentarily connect the auxiliary battery AB with the sectionrails. At the exit end of the section these auxiliary energy pulses pickup the detector relay KRZ in step therewith, it reourrently completesthe energizing circuit for the slow release approach relay AR and thatrelay, in turn, maintains the wayside signal S dark and keeps the tunedreed alternator` TA inactive'.

For prolonging the hold up time of detector relay KR! 'slightly' beyondthe instant at which the coding contact of device CR2 starts to movedownwardly at the end of each ofi code period, the stick winding 52 ofthe relay is providedy with a snubbing element 80'. This element isshown in the form of a rectifier which is so poled that it does notinterfere with the normal supply of current to the winding 52 but yetdoes provide a path fordischarge current incident to the co1- lapse offlux in tlie magnetic circuit of the relay following the vdisconnectionof the winding from its supply source.

The before stated effect of the snubbng element is to prolong the holdup time of the contacts of the relay KR2 at least until the Contact ofdevice CRZ has reached the lowermost position and thus connected thetracksrails I and 2 of the rear section with the track battery TB. Insonrie instances the hold up time may be even further prolonged untilthe track rails begin to transmit auxiliary energy from the entrance endbattery AB forwardly and over front contact 5 of yolf-vibe CE2 to thepick-upy Winding 5I of relay KRZ at thev section exit. In any case thisextension of hold up time reduces the amount of release delay with whichthe approach relay AR must be provided and thus' has the practicaleffect of quickening the response of that relay to the entry of a traininto the section.

In the event that a train approaches the signal location O of Fig. 5,the shu'nting action o-f its wheels and axles deprives the detectorrelay KRZ of the pick-up pulses of auxiliary energy and allows it torelease its contacts continuously.

Now continuously deenergized, relay AR releases and contact 9 thereofcompletes the before set up lighting circuit for the lamp G of theWayside signal So.` At the same time contact I I of relay KR completesthe operating circuit for the tuned alternator TA and thus causestransformer I1 to generate an output voltage of the l0() cycle persecond or other cab signal control frequency.

Each time now that the contacts 5 and 5u of the coding device CR2 are inthe lowermost positio-n this transformer I1 supplies the rails withalternating current energy over a circuit which extends from the rightterminal of the transformer secondary through conductor 51, the trackbattery TB, conductor y58, coding contacts 5 and I5 in parallel,conductors 59 and 28, track rail 2, the train wheels and axles (notshown), track rail I, conductor 33, impedance 21 and conductor 84 backto the left terminal of the transformer secondary. This alternatingcurrent energy is superimposed upon the direct currentsignal controlenergy from track battery TB which under all conditions reaches therails by way of a circuit extending from the positive terminal of thebattery, through conductor 56, back contacts 5 and 50 in parallel ofcoding relay CE2, conductors 55 and 28, the rails I and 2, conductor 33,impedance 2l, conductor 84, the secondary of transformer I'I andconductor 51 back to the negative terminal of battery TB.

The twor approach controlled signaling functions above discussedcontinue active until the rear of the departing train clears thelocation O. When that happens the rails I and 2 once more transmitauxiliary energy to the pick-up winding 5I of the detector relay KR2,that relay restores the recurrent energization of the approach relay AR,and it in turn picks up contacts 9 and i II to return the wayside signalSo and the tuned alternator TA to their normally inactive condition.

In the event that a second train approaches location O from the rearbefore the first train has movedvout ofthe track section ahead of thislocation, the cycle of operations just described will be repeated withthe single difference that instead of operating at the 180 pulse perminute rate the coding device CRZ will be operating at the rI5 pulse perminute rate. This means that prior to the entry of the second train intothe rear section the oif" period pulses of auxiliary energy are suppliedat a considerably slower rate of recurrence than under the 180 codeconditions previously described. However, the combined action of thestick and releasedelay circuits for the detector relay KR2 prolong eachof the pickup periods thereof until after the end of each of these offcode periods, thus reducing to somewhat less than the on periods of thecode the time between recurrent pulses of energication which aresupplied to the approach relay AR over contact I5.

As already stated, this relay AR is designed to have a slowness ofrelease which is adequate to bridge this maximum spacing interval. Underthe particularconditions assumed, however, the relay does not pick upfor the reason that as long as the forward train continues in thesection ahead of location O and releases decoding relay CRIB, contact'I2 of that relay interrupts the energizing circuit for the approachrelay and thus insures that the two approach controlled functionsalready named will be continued active.

In other words, the arrangement of Fig. 5- so operates that until therear of the forward train clears the exit end of the section of whichlocation O marks the entrance, the approach relay AR remains deenergizedeven though the detector relay KR2 responds in normal manner lto thereturn pulses of auxiliary energy which are received fromthe rearsection rails. As soon however, as the advance train does clear theforward section, the coding relay DR'I5 picks up contact I2 and relay ARthen becomes subject solely to the control of the contact I5 of thedetector relay KRZ.

It Will further be noted that in the representation of Fig. 5 thepolarities of the forward and the rear track sections are staggered.This staggering is for the purpose of providing the usual protectionagainst broken down rail joints in conventional manner. As has alreadybeen pointed out, however, the improved approach control facilitiesherein 'disclosed are operable with signaling systems which both do anddo not employ staggered polarities of adjacent track circuits.

Referring to Fig. 6, I have there represented a single signal location Qof a coded track circuit signaling system which employs decodingapparatus of a somewhat different form and with which the approachcontrol facilities just described in connection with Fig. 5 `arecombined. As in the equipments of the earlier figures, this signalingsystem is of the three indication type and it employs two differentsignal control codes produced by devices CTI and CTZ and respectivelyconsisting of 75 and 180 ener-gy pulses per minute.

As in the case of Fig. 5, the decoding equipment of Fig. 6 includes rstand second decoding relays DRIE and DRI 80 which respectively respond toboth of the 180 and the 75 pulse per minute trackway codes and to the180 code only. Decoding relay DRI80 is connected to receive energythrough a resonant o1' frequency selective unit DUIBII and from atransformer DT. This transformer is excited from any suitable directcurrent source over a pole changing contact 45 of the code followingtrack relay TR and by way of a circuit whichiincludes a conductor l8fIiand l a front contact 13 of the rst decoding relay DR15.

When arranged in the manner shown, this contact 13 disconnects thetransformer DT from its supply source whenever the track relay TR failsto respond to a trackway code, as when the track section ahead oflocation Q is occupied by a train. The same contact, moreover, rendersthe 75 code transmitter CTI inactive at all times that the named forwardsection is vacant.

The companion decoding relay DR15 of Fig. 6 is controlled by a contact46 of the track relay TR, which contact acts in cooperation with anassociated repeater relay FP. Both of the devices DR'I5 and FP are slowreleasing. As long as the track relay follows a code of the 75 pulse perminute or higher rate, recurrent pulses of energizing current from alocal direct current source are supplied to both the named relays. Inthe case ofrelay FP the circuit is completed by contact 46 when pickedup and in the case of relay DR'I5 the circuit is completed only whencontact 46 is released.

This latter circuit includes a front contact 81 of the repeater relay FParranged to insure that a continuously maintained condition of the trackrelay TR, either released or picked up, can never cause decoding relayDR`I5 to respond. When, however, the track relay operates Contact 46 incod-e following manner, the slow release repeater into two track circuitsections.

relay FP holds contact 81 picked up and thereby enables each release ofcontact 46 to complete the energizing circuit for the decoding relayjust named. In this manner, that relay DR15 picks up only when the trackrelay TR responds to coded energy of the 75 pulse per minute or higherrate.

As in the system of Fig. 5, the two decoding relays DR'I5 and DRI8U ofFig. 6 are provided with contacts 66 and 61 which control the waysidesignal -S at the same location. Moreover, relay DRI5 is provided with acontact 69 which selects which of the two code transmitters CI'I and CTZis to control the energizing circuit for Y the associated coding relayGRZ. This relay may or may not be provided with the snubbing facilitieswhich are represented at 'I6 in Fig. 5.

A further point of vdifference between the equipments of Figs. 6 and 5is `that in Fig. 6 a track transformer TT and a continuously availablesupply B-C of alternating current energy are employed for providing the.cab signal control code. In the form represented these particularfacilities are a duplicate of those of corresponding designations whichare represented in Fig. 4 and for this reason further descrip-tion isnot required. The mode of operation of the approach control facilitieswhich are represented in Fig. 6 in association with lthe just describedsignaling system decoding apparatus is so closely a duplicate` of thatalready described in connection with the equivalent equipment of Fig. 5as to require no further detailed description here.

Referring to Fig. 7, I have there represented cut section facilitieswhich are suitable for use with the approach control apparatus of theearlier described figures. Typically, as already explained, suchfacilities will be used when the main signal block length of track is,because of excessive length or for other reasons, divided In Fig. 7 thejunction of one point of such division is indicated at Qa.

As in the case of the corresponding cut section facilities of Fig 2,those represented in Fig. 7 perform three functions. First they repeataround the insulated joints 3 and into the rails of the section to therear of the cut the coded track circuit energy which is received fromthe rails of the forward section. Eifecting this first function isa codefollowing track relay TR2 which is operated by energy received from theforward rails, a `track battery TB which serves` as an energizing sourcefor the rails of the rear section, and coding contacts 5 and 5I! whichcomplete the rear section supply circuit each time that the relay TR2 ispicked up.

These coding contacts 5 and 5U correspond to the similarly identifiedmembers of each of Figs. 4, 5 and 6 and they differ therefrom in thatthey forma part of relay TR2 rather than of relay GRZ and in that therail supply circuit is completed when the contacts are in the uppermostrather than the lowermost position. In that event battery TB suppliesthe rails with current over a circuit which extends from the positiveterminal of the battery through conductor 56, front contact 5 of deviceySR2, conductor 28, track rail 2, rail I, conductor 33, impedance 2'I,the secondary winding ofthe track transformer TT, and conductor 51 backto the negative terminal of the battery TB. In this manner' each onperiod of signal control code received from the forward section isrepeated as an on period into the rails of the rear section and eachoif" period of the forward code is accompanied by an off period of therear section code. This arrangement Will be referred to as front contactcoding.

The second function performed by the cut section facilities of Fig. '7is to supply the forward section rails with` a pulse of auxiliary energyduring each off perio-d of the code to which relay TR2 responds.Participating in this second function is a source of auxiliary energyAB, an impulse relay IR which transfers the track circuit connectionfrom the operating Winding of relay TRR2 to battery AB, and atransformer RT which supplies relay IR with pick-up energy each timethat Contact I2 of relay TR2 releases. These `devices cooperate in themanner already explained in connection with Fig. 2 to perform the secondfunction named. f

The third function performed by the cut section facilities of Fig. 7 isto supply the rails of the rear section with coded alternating currentenergy suitable for cab signal control whenever a train enters that rearsection. Aiding in this third function is a track vtransformer TT, asupply circuit therefor including terminals B and C and controlled bycontact Il of a slow release approach relay AR, and means including acontact I5 0I" a detector relay KR2 for energizing relay AR in step withthe pulses of auxiliary energy which are received from the rear sectionrails.

As long as these pulses continue to be received relay AR is periodicallyenergized in` the manner already explained in connection with Figs. 4,

5 and 6, and contact Il thereof then remains picked up to maintaintransformer TT inactive. When, however, a train comes into the rearsection, relay RR continuously releases, relay AR is continuouslydeenergized, and contact Il thereof now releases to connect transformerTT with the alternating current source B-C and thus cause coding contact5 of device CR2`to impress the output of transformer TT upon the rearsection rails each time that the contact is in its uppermost position.

When in its lowermost position this same contact connects the pick-upwinding 5I of the detector relay KR2 in energy receiving relation withthe track rails. Likewise, when the second contact 50 of device CE2 isin the lowermost position` it sets up for the stick Winding 52 of therelay KR2 an energizing circuit which is completed when contact 6| ofthe same relay becomes picked up. Since the manner in. which thisdetector relay KR2 responds is no different than that in the earlierdescribed figures, no further description need be given here.

It will thus be seen that the cut section facilities of Fig. 7 may beinterposed within the limits of a signal block length of track withoutinterfering with the operation either of the main signaling scheme or ofthe improved approach control system of my invention which is usedtherewith. As shown in Fig. 7, the relative polarities of the two thereadjoining track circuits are staggered for the purpose of providing theusual protection against broken down rail joints,

Referring to Fig. 8, I have there represented cut section facilitieswhich are a duplicate of those shown in Fig. '7 with the exception thatthey are modified to provide back contact coding instead of the frontcontact coding. Here they supply circuit for the rear section rails iscompleted when the contacts 5 and 50 of device CRZ are in the releasedposition and the circuit is interrupted when the contacts are picked up.This means that each on period of the forward section code produces anoff period in the rear section code and that each off period of theforward section code is accompanied by an on period in the rear sectioncode.

The advantage of this back contact coding is that it compensates fordistortion of the track circuit code which accompanies its transmissionalong the length ofthe track circuit. The tendency of this distortion isto lengthen the olf periods and shorten the on periods and by repeatingthe coded energy around the insulated joints 3 (see Fig. '7) over theback contact of the track relay TR2 in the manner shown in Fig. 8, theabnormally long off periods are not amplifled but instead are convertedinto correspondingly longer on periods in the rear section. By the timethese have been transmitted to the exit end of the rear section thedistorting infiuence before referred to has a tendency to reduce them tothe desired condition of equality.

From the foregoing it will be seen that I have made importantimprovements in that scheme of approach control without line Wireswherein the rails of each unoccupied signal block length of tracktransmit code step pulses of auxiliary energy forwardly from the blockentrance to effect the energization of a slow release approach relay atthe block exit.

In particular, I have made provision for supplying the referred topulses of auxiliary energy to the entrance end of each track circuit inan improved manner which does not interfere with the normal codefollowing operation of the associated signaling system track relay andwhich eliminates all wastage of power at the location of that/relay; Ihave also made provision for receiving these pulses at the exit end ofthe signal block and for energizing the slow release approach relay instep with them in an improved manner which quickens the response of thatrelay to the entry of a train into the signal block; I have furtherextended the length of the track circuit which the nonline wireapparatus is capa- 'ole of approach controlling without the aid of cutsection facilities; I have additionally provided for a doublefunctioning of the contacts of the track circuit coding devices in theircontrol of the combined signaling and approach governing equipment whichis installed at the exit end of each signal block; and still further., Ihave -provided out section facilities which are suitable for use withapproach control means of the improved type herein disclosed.

As all` of these improvements are entirely a function of the trackcircuit and apparatus which is directly associated therewith, they areindependent of the coding and decoding facilities of the codingsignaling system and hence are usable with a Wide Variety of differenttypes and forms of such facilities.

While I have explained my invention in an application wherein both thelam-ps of the wayside signal and the supply of alternating current cabsignal energy are approach controlled, it will loe understood thateither one of these functions may be performed separately and that othercomparable functions may also be provided for in my new system.

Although I have herein shown and described only a few forms of approachcontrol apparatus embodying my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

'1. In combination with a section of track to the rails of which codedsignal control energy consisting of alternate on and oi periods iscontinuously supplied at the section exit and from the said rails ofwhich operating energy is received by a code following track relay atthe section entrance, approach control facilities comprising a source'ofauxiliary energy, means governed by said track relay for disconnectingsaid rails from the operating winding of that relay and for connectingthem with said yauxiliary energy source during each of the said offperiods of the signal control code whi-ch is received by the track relaywhereby those rails are supplied with a pulse of auxiliary energy uponthe occasion of each of said connections, a slow release approach relayat the section exit, means for energizing said approach relay in stepwith the said pulses of auxiliary energy which are received from saidrails at the said section exit whereby to maintain that relayvcontinuously picked up as long as said section is unoccupied, andtraiTic controlling apparatus governed by said approach relay andrendered active when that relay releases in response to the presence ofa train in said section.

2. In combination with a section of track to the rails of which codedsignal control energy consisting of alternate on and ofi periods iscontinuously supplied and with the said rails of which the operatingwinding of a `code following track relay is connected, approach controlfacilities comprising a source of auxiliary energy, means governed bysaid track relay for transferring said track rail connection from theoperating winding of that relay to said auxiliary energy source at thebeginning of each of the said ofi periods of the received signal controlcode and for returning that connection to the track relay winding beforethe beginning of the next on period of that code whereby to cause saidrails to be supplied with a. pulse of auxiliary energy during each ofthose oft periods, a slow release approach relay installed at thesection exit and energized in step with the said pulses of auxiliaryenergy which are there received from the section rails whereby to bemaintained continuously picked up. as long as said section is vacant andto release when a train comes into the section, and tra-nic governingapparatus controlled by said approach relay.

3. In a railway signaling system which includes a section of track tothe rails of which coded track circuit energy consisting of alternate jon" and 01T periods is continuously supplied and from the said rails ofwhich operating energy is received by a code following track relay atthe section entrance, the combination of approach control facilitiescomprising a source of auxiliary energy, an impulse relay effective whenenergized to disconnect the rails of said section from the operatingwinding of the track relay and to connect them with said auxiliaryenergy source whereby to cause said rails then to receive a pulse ofauxiliary energy, means controlled by said track relay for energizingsaid impulse relay at the beginning of each of the said o periods of thereceived track circuit code, a slow release approach relay installed atthe exit end of the section and energized in step with the vsaid pulsesof auxiliary energy which are there received from the section railswhereby to be maintained continuously picked up asi long as said sectionis vacant andto release when a train comes into the section, and trainogoverning apparatus controlled by said approach relay.

4. In combination, a section of railway track, means for supplying codedenergy to the rails of said section, a code following track relay havingan operating winding connected with said rails, a source oi auxiliaryenergy, an impulse relay for transferring the track rail connection fromsaid track relay winding to said auxiliary energy source, meanscontrolled by said track relay for momentarily energizing said impulserelay each time that the track relay releases whereby to cause saidrails then to receive a pulse auxiliary energy, a slow release approachrelay energized in step with the said pulses of auxiliary energy whichare received from the section rails whereby to be maintainedcontinuously picked up as long as said section is vacant and to releasewhen a train comes into the section, and traiTic governing apparatuscontrolled by said approach relay.

5,-In combination with a section of railway traok which forms a part ofa railway signaling system of the -coded track circuit class, approachcontrol facilities comprising a source of trackway energy at the exitend of the section, an approach governing relay also located at thesection exit, a coding contact which repeatedly connects the rails ofsaid section first to said trackway energy source and then to saidapproach governing relay and thereby produces a trackway code consistingof alternate on and oil periods the latter of which coincide with saidapproach governing relay connections, a code following track relaylocated at the entrance end of the section and having an operatingwinding which is connected with said rails, a source` of auxiliaryenergy also located at said section entrance, means controlled by saidtrack relay for disconnecting the section rails from said operatingwinding of the track relay and for connecting them with said auxiliaryenergy source during each of the said off periods of said trackway codewhich is received by the track relay whereby to cause said rails toreceive a pulse of auxiliary energy during each of those off periods andto transmit that pulse forwardly' to said approach governing relay at.the section exit, and traic governing apparatus controlled by saidapproach governing relay and rendered active when and only when thatrelay is deprived of said recurring pulses of auxiliary energy by therail shunting action of a train within said section.

6. In combination with a section of track to the rails of which codedsignal -control energy consisting of alternate on and oft periods iscontinuously supplied and with the said rails of which a code followingtrack relay is connected,

approach control facilities comprising a source of auxiliary energy,means governed by said track relay for transferring said track railconnection from the operating winding of that relay to said auxiliaryenergy source at the beginning of each of the said oii periods of thereceived signal control code and for returning that connection to thetrack relay winding before the beginning of the succeeding on" period ofthat code whereby to cause saidrails to be supplied with a pulse ofauxiliary energy during each of those 01T periods, and trafficcontrolling apparatus at the exit end of said section governed by saidcode step pulses of auxiliary energy and rendered inactive as long asthose pulses are there received from said rails. l

emes

97. In a railway signaling system which includes a section of track tothe rails of which coded signal control energy consisting of alternateon and off periods is continuously supplied and with the said rails ofwhich a code following track relay is connected, the combination ofmeans at the entrance end of said section for supplying a pulse ofauxiliary energy to said rails during each of the said off periods ofthe signal control code which is received by the track `relay comprisinga source of auxiliary energy, an impulse relay effective when energizedto disconnect the section rails from said track relay and to ,connectthem with said auxiliary energy source whereby to cause those rails thento receive a pulse of auxiliary energy, and means controlled by saidtrack relay for momentarily energizing said impulse relay at thebeginning of each of said off code periods; and traffic controllingapparatus at the exit end of said section governed by said code steppulses of auxiliary energy which are transmitted thereto over said railsand rendered inactive as long as said transmission of those pulsescontinues.

8. In combination with a section of track to the rails of which codedsignal control energy consisting of alternate "on and olf periods iscontinuously supplied and with the said rails of which a code followingtrack relay is connected, approach control facilities comprising asource of auxiliary energy, an impulse relay `effective when energizedto transfer said track rail connection from said track relay to saidauxiliary energy source, a transformer connected in energy supplyingrelation with said impulse relay, a direct current exciting circuit forsaid transformer which is controlled by a contact of said track relay insuch manner that that transformer supplies a momentary pulse of pick-upenergy to said impulse relay at the beginning of each of the said offperiods of the received signal control code and thereby causes saidsection rails then to receive a pulse of auxiliary energy, and trafccontrolling apparatus at the exit end of said section governed by saidcode step pulses of auxiliary energy which are there received from saidrails.

9. In combination, a section of railway track, means for supplying codedsignal control energy to the rails of said section, a code followingtrack relay having an operating winding which is con- 2 nected with saidrails, a source of auxiliary energy, an impulse relay effective whenenergized to disconnect the section rails from said track relay windingand to connect them with said auxiliary energy source, a transformerconnected in energy supplying relation with the operating winding ofsaid impulse relay, a direct current exciting circuit for saidtransformer which includes a contact of said track relay, and which isso Aarranged that that transformer supplies a ,momentary pulse of.pick-up' energy to said impulse relay each time that the track relayreleases and thereby causes said section rails then to receive a pulseof auxiliary energy, and traffic controlling apparatus 'at the exit endof said section governed by the said auxiliary energy which is therereceived from said rails.

l0. In combination, a section of railway track, means for supplyingcoded signal control energy to the lrails of said section, a codefollowing track relay vhaving an operating winding which is connectedwith said rails, a source of auxiliary energy,

an impulse relay effective when energized in the normal polarity`direction to disconnect the section rails from said track relay windingand to connect them with said auxiliary energy source, a transformerconnected in energy supplying relation with said impulse relay, a directcurrent exciting circuit for said transformer, a contact of said track`relay included in said circuit for the purpose of causing thetransformer to generate a pulse of normal polarity output voltage eachtime that the track relay releases whereby to produce a response by saidimpulse relay which causes said section rails then to receive a pulse ofauxiliary energy, and traiiic controlling apparatus at the exit end ofsaid section governed by the said auxiliary energy which is therererceived from said rails.

1l. In combination with a section of track to the rails of which codedsignal control energy is continuously supplied and with the said railsof which a code following track relay is connected, approach controlfacilities comprising a source of auxiliary energy, an impulse relayeffective when energized in the normal polarity direction to transfersaid track rail connection from said track relay to said auxiliaryenergy source, a decoding transformer provided with a direct currentexciting circuit which is controlled by said track relay, a secondarywinding of said transformer connected to impress a pulse of normalpolarity voltage upon the operating winding of said impulse relay eachtime that said track relay releases whereby to produce a response bysaid impulse relay which causes said section rails then to receive apulse of auxiliary energy, and traffic controlling apparatus at the exitend of said section governed by the said auxiliary energy which is therereceived from said rails.

12. In combination with a section of track which forms a part of arailway signaling system of the coded track circuit class, approachcontrol facilities comprising a direct current source of trackway energyat the section exit, a code following detector relay, a continuouslyoperating coding contact which repeatedly connects 'the rails of said`section first with said energy source and then with the Winding of saiddetector relay and thereby produces a direct current trackway codeconsisting of alternate on and off periods the .latter of which coincidewith said detector relay connections, means for supplying said railswith a pulse of auxiliary energy during each of the said off periods ofthe said direct current trackway code which is received at the sectionentrance whereby those rails transmit each of those pulses forwardly tosaid detector relay and thus cause that relay to follow code as long assaid section is unoccupied, a slow release approach relay energized instep with the responses of said detector relay and maintained picked upby that energization as long as the detector relay continues to followcode, and means at the section exit for locally generating analternating current voltage and for superimposing said voltage upon saiddirect current trackway code whenever said approach relay becomesreleased in response to the presence of a train in said section.

,13. In combination with a section of track which forms a part of arailway signaling system of the coded track circuit class, approachcontrol facilities comprising a source of direct current energy at thesection exit, a code following detector relay, a continuously operatingcoding device having a contact which repeatedly connects the rails ofsaid section first with said energy source and then with the winding ofsaid detector relay and thereby produces a direct curlong as saidsection is unoccupied, a slow release approach relay energized in stepwith the responses of said detecte-r relay and maintained picked up bythat energization as long as the detector relay continues to followcode, and means at the section exit for converting energy from saiddirect current source into an alternating current voltage and foi`superimposing said voltage upon said direct current trackway codewhenever said approach relay becomes released in response to thepresence of a train in saidi section,

14. In combination with a section of track to the rails of which codedsignal control energy consisting of alternate on and oi periods iscontinuously supplied, approach control facilitiesI comprising a codefollowing pilot relay connected with said rails at the section entranceand arranged to be operated by the said coded energy which is receivedfrom those rails,l a code following track relay locally energized over acontact of said pilot relay and arranged to duplicate the code followingoperations of the pilot relay, a source of auxiliary energy, meansgoverned by said track relay for disconnecting said track rails from theoperating winding of said pilot relay and for connecting them with saidauxiliary energy source during each of said off periods of the receivedsignal control code whereby to cause those rails to receive a pulse ofauxiliary energy during each of those off periods, a slow releaseapproach relay installed at the section exit and energized in step withthe pulses of auxiliary energy which are there received from the sectionrails whereby to be maintained picked up as long as said section remainsvacant and to release when a train comes into the section, and trafficgoverning apparatus controlled by said approach relay.

l5. In a railway signaling system which includes a section of track tothe rails of which coded track circuit energy consisting of alternate onand off periods is continuously supplied, the combination of approachcontrol facilities comprising a code following pilot relay connectedwith said rails at the section entrance and arranged to be operated bythe said coded energy which is received from those rails, a codefollowing track relay locally energized over a contact of said pilotrelay and arranged to duplicate the code following operations of thepilot relay, a source of auxiliary energy, an impulse relay effectivewhen energized to disconnect the rails of said section from ytheoperating Winding of the pilot relay and to connect them with saidauxiliary energy source. means controlled by said track relay formomentarily energizing said impulse relay at the beginning of each ofthe said off periods of the received signal control code whereby toproduce a response by said impulse relay which causes said section railsthen to receive a pulse of auxiliary energy, a slow release approachrelay located at the exit end of the section and energized in step withthe pulses of auxiliary energy which are there received from the sectionrails whereby to be maintained picked up as long' as said sectionremains vacant and to release when a train comes into the section, andtrafiic governing apparatus controlled by said approach relay.

16. In combination, a section of railway track, means yfor supplyingcoded signal control energy to the rails of said section, a codefollowing pilot relay having an operating winding which is connectedwith said rails, said pilot relay following the coding of the saidsignal control energy which is received from those rails, a codefollowing track relay locally energized over a Contact of said pilotrelay and arranged to duplicate the code following operations of thepilot relay, an impulse relay effective when energized inthe normalpolarity direction to disconnect the section rails from said track relayWinding and to connect them with said auxiliary energy Source, atransformer connected in energy supplying relation with said impulserelay, a direct current exciting circuit for said transformer, a contactof said track relay included in said circuit for the purpose of causingthe transformer to generate a pulse of normal polarity output voltageeach time that the track relay releases whereby to produce a response bysaid impulse relay which causes said section rails. then to receive apulse of auxiliary energy, and traffic controlling apparatus at the exitend of said section governed by the said auxiliary energy which is therereceived from said rails.

17. In combination with a section of railway track, a source of energyfor the rails of said section, a code following detector relay providedwith a pick-up circuit and with a stick circuit, a continuouslyoperating coding device, means including a first contact of said devicefor repeatedly connecting the track section rails first to said energysource and then to said relay pickup circuit, means effective undervacant conditions of said track section for supplying said rails with apulse of auxiliary energy during each period that said pick-up circuitis connected with those rails whereby to cause said detector relayrecurrently to pick up as long as the track section remains vacant,means including a second contact of said coding device for completingsaid stick circuit from the time of each pick up of the detector relayuntil the end of the code period within which that pick up occurswhereby to prolong the hold-up time of that relay for the full durationof each of said code periods, means for causing said second contact ofthe coding device to act in parallel with said first contact thereof inmaking and breaking the connection .of said track rails with said energysource whereby to reduce the duty imposed upon said first contact, andtrailic. controlling apparatus governed by said detector relay andrendered active when and only when the said pick-up circuit of thatrelay is deprived of said recurring pulses of auxiliary energy by therail shunting action of a train within said section.

18. In combination, a section of railway track, means for supplying therails'of said section with coded signal control energy which consists ofalternate on and off periods, means effective under vacant conditions ofthe section for also supplying said rails with a pulse ofv auxiliaryenergy during each of the said olf periods of said signal control code,a code following detector provided with a lpick-up circuit and with astick circuit, means for connecting said pick-up circuit in energyreceiving relation with the section rails during each of said off codeperiods whereby said auxiliary energy picks up the detector relay duringeach of those periods as long as said section remains vacant, a slowrelease approach relay energized in step with the responses of saiddetector relay and thereby maintained picked up as long as the detectorrelay follows code, means for completing said stick circuit of thedetector relay from the time of each pick up of that relay until the endof the off code period within which that pick up occurs whereby toprolong the energization of said detector relay for the full duration ofeach of said H periods, means for delaying the release of the detectorrelay beyond each interruption of its said stick circuit whereby toreduce the delay period of said approach relay which is necessary tospan the intervals between said recurrent responses of said detectorrelay, and traffic controlling apparatus governed by said approach relayand rendered active when that relay releases in response to the railshunting action of a train within said section.

19. In combination, a section oi railway track, means for supplying therails of said section with coded signal control energy which consists ofalternate on and "01T" periods, means effective under vacant conditionsof the section for also supplying said rails with a pulse of auxiliaryenergy during each of the said off periods of the signal control code, acode following detector relay provided with a pick-up winding and with astick winding, means for connecting said pickup winding across saidrails during each of the said 01T code periods whereby to supply saidauxiliary energy to that winding and thereby pick up the detector relay,a source of stick energy,

means for connecting said stick winding to said source from the time ofeach pick-up of the detector relay until the end of the said ofi codeperiod within which that response occurs whereby to prolong the hold-uptime of said detector relay for the full duration of each of said oiperiods, a slow release approach relay energized in step with theresponses of said detector relay and thereby maintained picked up aslong as the detector relay follows code, a snubbing impedance bridgedacross said stick Winding to impart slow release characteristics to thedetector relay whereby to reduce the delay period of said approach relaywhich is necessary to span the intervals between said recurrentresponses of said detector relay, and traflic 'controlling apparatusgoverned by said approach relay and rendered active when that relayreleases in response to the rail shunting action of a train within saidsection. i

20. In combination with adjoining forward and rear sections of railwaytrack, means for supplying the rails of said forward section withrecurrent on" and off periods of energy coded at a high speed rate undercertain conditions and at -a low speed rate under other conditions, acode following track relay connected with said forward section rails atthe entrance end of the section, a source of auxiliary energy, meansgoverned by said track relay for disconnecting said rails from thatrelay -and for connecting them with said auxiliary energy source duringeach of the said off periods of the received trackway code, a. firstdecoding relay controlled by said track relay and arranged to respondwhen the track relay is following either of said two trackway codes, asecond decoding relay also controlled by said track relay but arrangedto CII respond to said high speed code only, a normally inactive waysidesignal positioned at the entrance of said forward section of track andcontrolled byy said two decoding relays, and an approach relay arrangedto render said signal active whenever a train enters said rear sectionof track.

2l. In combination with adjoining forward and rear sections of railwaytrack, means for supplying the rails of said forward section with energycoded at a high speed rate or at a low speed rate, a code followingtrack relay operated by energy received from said forward section rails,a rst decoding relay controlled by said track relay and responsive toeither of said two trackway codes, a second decoding relay alsocontrolled by said track relay but responsive to said high speedcodeonly, a normally inactive wayside signal located at the entrance of saidsection and controlled by said two decoding relays, means controlled bysaid rst decoding relay for supplying the rails of said rear tracksection with recurrent "on and oi periods of energy coded at said highspeed rate or at said low speed rate, means for also supplying said rearsection rails with a pulse of auxiliary energy during each of said offperiods of the trackway code which is received at -th-e entrance of therear section, a code following detector relay responsive to said codestep pulses of auxiliary energy which are received from said rearsection rails at the exit ofthe rear section, a slow release approachrelay locally energized in step with the responses of said detectorrelay and arranged to render said signal active whenever `said reartrack section is occupied, and means controlled by said irst decodingrelay for interrupting the energizing circuit for said approach relayand thereby also rendering said signal active whenever'said forwardsection is occupied.

22. In combination, a track section divided from the remaining track Ibyinsulating joints, a source of track circuit current at each end of saidsection, a track relay for each end of said section, movable contactmeans at each end of said section for connecting either the source oftrack circuit current or the track relay at such en`d across the trackrails but not both, means for causing intermittent operation of saidcontact means so that the track relay at one end and the track circuitsource at the other end and the track relay at said other end and thetrack circuit source at said one end are alternately connected to thetrack rails, whereby two track circuits are alternately established onthe same track section, and signals controlled by said track relays. v

23. In combination; a track section divided from the remaining track -byinsulating joints; a source of track circuit current at each end of saidsection; a track relay for each end of said section; movable contactmeans at each end of said section for connecting either the source roftrack circuit current or the track relay at such `end across the trackrails but not both; means for causing intermittent operation of saidcontact means to establish track circuits alternately, one track circuitof which includes the source of track circuit current at one end, thetrack rails and the track relay at the other, and the other trackcircuit of which includes the source of track circuit current at theother end, the track rails and the track relay at said one end.

HERMAN G. BLOSSER.

